1. Field of the Invention
The present invention relates to an improvement in a continuously variable transmission apparatus utilized as an automatic transmission for a vehicle (automobile) and integrated with a toroidal-type continuously variable transmission apparatus realizing a structure capable of preventing a state of bringing about an abrupt variation in a transmission ratio when switching a low speed mode and a high speed mode at low cost.
2. Background Art
As an automatic transmission apparatus for a vehicle, researches are carried out on using a toroidal-type continuously variable transmission as shown by FIGS. 16 through 18 and the transmission is partially embodied. The toroidal-type continuously variable transmission is referred to as a double cavity type and input side disks 2, 2 are supported by surroundings of both end portions of an input shaft 1 via ball splines 3, 3. Therefore, the two input side disks 2, 2 are supported concentrically and synchronizingly rotatably. Further, an output gear 4 is supported at a surrounding of a middle portion of the input shaft 1 rotatably relative to the input shaft 1. Further, output side disks 5, 5 are engaged to both end portions of a cylindrical portion provided at a central portion of the output gear 4 respectively by splines. Therefore, the two output side disks 5, 5 are synchronizingly rotated along with the output gear 4.
Further, respective pluralities of pieces (normally, two through three pieces respectively) of power rollers 6, 6 are interposed between the respective input side disks 2, 2 and the respective output side disks 5, 5. The respective power rollers 6, 6 are respectively supported rotatably by inner side faces of trunnions 7, 7 via support shafts 8, 8 and a plurality of rolling bearings. The respective trunnions 7, 7 are rockably displaceable centering on pivoting shafts 9, 9 provided at the respective trunnions 7, 7 concentrically with each other at both end portions in respective length directions (up and down direction of FIGS. 16, 18 and head and tail direction of FIG. 17). A motion of inclining the respective trunnions 7, 7 is carried out by displacing the respective trunnions 7, 7 in axial directions of the pivoting shafts 9, 9 by hydraulic type actuators 10, 10 and inclined angles of all of the trunnions 7, 7 are synchronized with each other hydraulically and mechanically.
That is, when the inclined angles of the respective trunnions 7, 7 are changed in order to change a transmission ratio between the input shaft 1 and the output gear 4, the respective trunnions 7, 7 are displaced by the respective actuators 10, 10 respectively in reverse directions (same direction with regard to directions of rotating the respective disks 2, 5), for example, the power roller 6 on a right side of FIG. 18 is displaced to a lower side of the drawing and the power roller 6 on a left side of the drawing is displaced to an upper side of the drawing respectively. As a result, directions of forces in tangential lines operated to contact portions between peripheral faces of the respective power rollers 6, 6 and the inner side faces of the respective input side disks 2, 2 and the respective output side disks 5, 5 are changed (side slip is produced at the contact portion). Further, in accordance with the change in the directions of the forces, the respective trunnions 7, 7 are rocked (inclined) indirections reverse to each other centering on the pivoting shafts 9, 9 axially supported by support plates 11, 11. As a result, contact positions between the peripheral faces of the respective power rollers 6, 6 and the inner side faces of the respective input side and output side disks 2, 5 are changed and a rotational transmission ratio between the input shaft 1 and the output gear 4 is changed.
A state of charging and discharging a pressurized oil to and from the respective actuators 10, 10 is controlled by a single piece of control valve 12 regardless of a number of the respective actuators 10, 10 and movement of any single piece of trunnion 7 is fed back to the control valve 12. The control valve 12 includes a sleeve 14 displaced by a stepping motor 13 in an axial direction (head and tail direction of FIG. 16, left and right direction of FIG. 18) and a spool 15 fit to an inner diameter side of the sleeve 14 displaceably in the axial direction. Further, in rods 17, 17, connecting the respective trunnions 7, 7 and pistons 16, 16 of the actuators 10, 10, an end portion of the rod 17 belonging to any single piece of the trunnion 7 is fixed with a precess cam 18 and there is constituted a feedback mechanism for transmitting movement of the rod 17, that is, a synthesized value of a displacement amount in an axial direction and a displacement amount in a rotational direction to the spool 15 via the precess cam 18 and a link arm 19. Further, a synchronizing cable 20 is hung between the respective trunnions 7, 7 to thereby mechanically synchronize the inclined angles of the respective trunnions 7, 7 even in a failure in a hydraulic system.
In switching a speed changing state, a flow path in a predetermined direction of the control valve 12 is opened by displacing the sleeve 14 to a predetermined position compatible with a desired transmission ratio by the stepping motor 13. As a result, a pressurized oil is fed in the predetermined direction to the respective actuators 10, 10 and the respective actuators 10, 10 displace the trunnions 7, 7 in the predetermined direction. That is, in accordance with feeding the pressurized oil, the respective trunnions 7, 7 are rocked centering on the respective pivoting shafts 9, 9 while being displaced in axial directions of the respective pivoting shafts 9, 9. Further, movement (in axial direction and rocking displacement) of any single piece of the trunnion 7 is transmitted the spool 15 via a cam surface 21 of the precess cam 18 fixed to the end portion of the rod 17 and the link arm 19 to displace the spool 15 in the axial direction. As a result, in a state of displacing the trunnion 7 by a predetermined amount, the flow path of the control valve 12 is closed and the pressurized oil is stopped from charging and discharging to and from the respective actuators 10, 10.
In operating the above-described toroidal-type continuously variable transmission, the input side disk 2 on one side (left side of FIGS. 16, 17) is driven to rotate by a drive shaft 22 connected to a power source of an engine or the like via a press apparatus 23 of a loading cam type, or a hydraulic type as illustrated. As a result, the pair of input side disks 2, 2 supported by the both end portions of the input shaft 1 are rotated synchronizingly while being pressed in directions proximate to each other. Further, the rotation is transmitted to the respective output side disks 5, 5 via the respective power rollers 6, 6 and outputted from the output gear 4.
In the case in which rotational speeds of the input shaft 1 and the output gear 4 are changed, first, when the speed is reduced between the input shaft 1 and the output gear 4, the respective trunnions 7, 7 are moved in the axial directions of the respective pivoting shafts 9, 9 by the respective actuators 10, 10 to rock to positions shown in FIG. 17. Further, as shown by FIG. 17, the peripheral faces of the respective power rollers 6, 6 are made to be respectively brought into contact with portions of the respective input side disks 2, 2 on sides of centers of the inner side faces and portions of the respective outputs side disks 5, 5 on sides of outer peripheries of the inner side faces. On the contrary, in increasing the speed, the respective trunnions 7, 7 are rocked in directions opposed to those of FIG. 17 and contrary to a state shown in FIG. 17, the respective trunnions 7, 7 are inclined such that the peripheral faces of the respective power rollers 6, 6 are respectively brought into contact with portions of the respective input side disks 2, 2 on sides of the outer peripheries in the inner side surfaces thereof and portions of the respective output side disks 5, 5 on sides of the centers of the inner side faces thereof. A middle transmission ratio (speed ratio) is provided between the input shaft 1 and the output gear 4 when the inclined angles of the respective trunnions 7, 7 are set to middles.
Further, when the toroidal-type continuously variable transmission constituted and operated as described above is actually integrated to a continuously variable transmission for an automobile, it has been variously proposed in a background art to constitute a continuously variable transmission apparatus by being integrated with a planetary gear mechanism. FIG. 19 shows the continuously variable transmission apparatus proposed in the prior art disclosed in U.S. Pat. No. 6,251,039. The continuously variable transmission apparatus is referred to as so-to-speak geared neutral, in which a rotational state of an output shaft can be switched to rotate regularly and rotate reversely by interposing a stationary state while rotating the input shaft in one direction and which is constituted by a toroidal-type continuously variable transmission 24 and a planetary gear type transmission 25. The toroidal-type continuously variable transmission 24 is provided with the input shaft 1, the pair of input side disks 2, 2, the output side disk 5a and the plurality of power rollers 6, 6. In the illustrated example, the output side disk 5a is constituted by a structure of butting outer side faces of the pair of output side disks to integrate.
The planetary gear type transmission 25 is provided with a carrier 26 coupled to fix to the input shaft 1 and the input side disk 2 on one side (right side of FIG. 19). A first transmitting shaft 28 both end portions of which are respectively provided fixedly with planetary gear elements 27a, 27b is rotatably supported by a middle portion in a diameter direction of the carrier 26. Further, a second transmitting shaft 31 both end portions of which are fixedly provided with sun gears 29a, 29b is supported rotatably on a side opposed to the input shaft 1 by interposing the carrier 26 therebetween concentrically with the input shaft 1. Further, each of the planetary gear elements 27a, 27b and a sun gear 32 fixedly provided to a front end portion (right end portion of FIG. 19) of a hollow rotating shaft 32 abase end portion (left end portion of FIG. 19) is coupled with the output side disk 5a or the sun gear 29a fixedly provided to one end portion (left end portion of FIG. 19) of the second transmitting shaft 30 are respectively brought in mesh with each other. Further, the planetary gear element 27a on one side (left side of FIG. 19) is brought in mesh with a ring gear 34 rotatably provided at a surrounding of the carrier 26 via other planetary gear element 33.
Meanwhile, planetary gear elements 36a, 36b are rotatably supported by a second carrier 35 provided at a surrounding of the sun gear 29b fixedly provided to other end portion (right end portion of FIG. 19) of the second transmitting shaft 30. Further, the second carrier 35 is fixedly provided to a base end portion (left end portion in FIG. 19) of an output shaft 37 arranged concentrically with the input shaft 1 and the second transmitting shaft 30. Further, the respective planetary gear elements 36a, 36b are brought in mesh with each other, the planetary gear element 36a on one side is brought in mesh with the sun gear 29b, and the planetary gear element 36b on other side is brought in mesh with a second ring gear 38 provided rotatably at a surrounding of the second carrier 35, respectively. Further, the ring gear 34 and the second carrier 35 are made to be engageable and disengageable by a low speed clutch 39, and the second ring gear 38 and a fixed portion of a housing or the like are made to be engageable and disengageable by a high speed clutch 40.
In the case of the above-described continuously variable transmission apparatus shown in FIG. 19, in a so-to-speak low speed mode state connecting the low speed clutch 39 and disconnecting the high speed clutch 40, power of the input shaft 1 is transmitted to the output shaft 37 via the ring gear 34. Further, by changing a transmission ratio of the toroidal-type continuously variable transmission 24, a transmission ratio as a total of the continuously variable transmission apparatus, that is, a transmission ratio between the input shaft 1 and the output shaft 37 is changed. In such a low speed mode state, the transmission ratio of the total of the continuously variable apparatus is changed infinitely. That is, by adjusting the transmission ratio of the toroidal-type continuously variable transmission 24, while bringing the input shaft 1 in a state of being rotated in one direction, a rotational state of the output shaft 37 can be converted to regular rotation and reverse rotation by interposing a stationary state.
Further, in running at an accelerated speed or a constant speed in such a low speed mode state, a torque (passing torque) passing the toroidal-type continuously variable transmission 24 is applied from the input shaft 1 to the output shaft disk Sa via the carrier 26, the first transmitting shaft 28, the sun gear 32 and the hollow rotating shaft 31 and is applied from the output side disk Sa to the respective input side disks 2, 2 via the respective power rollers 6, 6. That is, the torque passing the toroidal-type continuously variable transmission 24 in running at the accelerated speed or the constant speed is circulated in a direction in which the respective input side disks 2, 2 receive the torque from the respective power rollers 6, 6.
In contrast thereto, in a so-to-speak high speed mode state in which the low speed clutch 39 is disconnected and the high speed clutch 40 is connected, the power of the input shaft 1 is transmitted to the output shaft 37 via the first and the second transmitting shafts 28, 30. Further, by changing the transmission ratio of the toroidal-type continuously variable transmission 24, the transmission ratio as the total of the continuously variable transmission apparatus is changed. In this case, the larger the transmission ratio of the toroidal-type continuously variable transmission 24, the larger the transmission ratio of the total of the continuously variable transmission apparatus. In running at an accelerated state or a constant speed in such a high speed mode state, a torque passing the toroidal-type continuously variable transmission 25 is applied from the respective input side disks 2, 2 to the output side disk 5a via the respective power rollers 6, 6.
Further, U.S. Pat. No. 6,171,210 discloses a continuously variable transmission apparatus as shown by FIG. 20. The continuously variable apparatus is referred to as so-to-speak power split type and constituted by combining a toroidal-type continuously variable transmission 24a and a planetary gear type transmission 25a. Further, in a low speed mode, power is transmitted only by the toroidal-type continuously variable transmission 24a and in a high speed mode, power is mainly transmitted by the planetary gear type transmission 25a and a transmission ratio by the planetary gear type transmission 25a is controlled by changing a transmission ratio of the toroidal-type continuously variable transmission 24a. 
Therefore, a base end portion (right end portion of FIG. 20) of the input shaft 1 that extends through the center portion of the toroidal-type continuously variable transmission 24a and supports the pair of input side disks 2, 2 at both end portions thereof and a ring gear 41 constituting the planetary gear type transmission 25a are coupled via the high speed clutch 40a. Further, a starting clutch 44 and a hydraulic type pressing apparatus 23a are provided in a direction of transmitting power in series with each other between an output side end portion (right end portion of FIG. 20) of a crankshaft 43 of an engine 42 constituting a drive source and an input side end portion (=base end portion=left end portion of FIG. 20) of the input shaft 1. The pressing apparatus 23a is constituted by fitting the input side disk 2 on the base end side into a cylinder 96 in oil tight and to be able to transmit a rotating force.
Further, an output shaft 37a for outputting power based on rotation of the input shaft 1 is arranged concentrically with the input shaft 1. Further, the planetary gear type transmission 25a is provided at a surrounding of the output shaft 37a. A sun gear 45 constituting the planetary gear type transmission 25a is fixed to an input side end portion (left end portion of FIG. 20) of the output shaft 37a. Therefore, the output shaft 37a is rotated in accordance with rotation of the sun gear 45. The ring gear 41 is supported at a surrounding of the sun gear 45 concentrically with the sun gear 45 and rotatably. Further, a plurality of sets of planetary gear elements 46a and 46b are provided between an inner peripheral face of the ring gear 41 and an outer peripheral face of the sun gear 45. The respective sets of the planetary gear elements 46a and 46b are brought in mesh with each other, the planetary gear elements 46a arranged on an outer diameter side are brought in mesh with the ring gear 41 and the planetary gear elements 46b arranged on an inner diameter side are brought in mesh with the sun gear 45. The respective planetary gear elements 46a and 46b are rotatably supported by a carrier 47. Further, the carrier 47 is rotatably supported by a middle portion of the output shaft 37a. 
Further, the carrier 47 and the pair of output side disks 5, 5 constituting the toroidal-type continuously variable transmission 24a are connected in a state of being capable of transmitting the rotating force by a first power transmitting mechanism 48. The first power transmitting mechanism 48 is constituted by coupling both end portions of a transmitting shaft 49 and the respective output side disks 5, 5 or the carrier 47 by a chain transmitting mechanism or a gear transmitting mechanism. Further, the carrier 47 is rotated by a speed in accordance with a transmission ratio of the chain transmitting mechanism or the gear transmitting mechanism in accordance with rotation of the respective output side disks 5, 5 in a direction reverse to that of the output side disks 5, 5. Meanwhile, the input shaft 1 and the ring gear 41 are made to be connectable in a state of capable of transmitting the rotating force via other transmitting shaft 50 disposed concentrically with the input shaft 1 and the high speed clutch 40a. That is, the transmitting shaft 50 is rotated in a direction and at a speed the same as those of the input shaft 1 in connecting the high speed clutch 40a. 
Further, a low speed clutch 39a is provided between an outer peripheral edge portion of the carrier 47 and one end portion (right end portion of FIG. 20) in the axial direction of the ring gear 41. Further, a reverse clutch 51 is provided between the ring gear 41 and a fixed portion of a housing (not illustrated) of the continuously variable transmission apparatus or the like.
According to the continuously variable transmission apparatus constituted as described above, first, in the low speed mode state, the low speed clutch 39a is connected and the high speed clutch 40a and the reverse clutch 51 are disconnected. When the starting clutch 44 is connected under the state and the input shaft 1 is rotated, only the toroidal-type continuously variable transmission 24a transmits power from the input shaft 1 to the output shaft 37a. In running at low speed in this way, the transmission ratio between the respective pairs of input side disks 2, 2 and the output side disks 5, 5 is controlled similar to the case of a single one of the above-described toroidal-type continuously variable transmission shown in FIGS. 16 through 18. Further, in accelerating or running at constant speed in the above-described low speed mode state, a torque passing the toroidal-type continuously variable transmission 24a is transmitted from the respective above-described input side disks 2, 2 to the respective above-described disks 5, 5 via the respective power rollers.
In contrast thereto, in the high speed mode state, the above-described high speed clutch 40a is connected and the above-described low speed clutch 39a and the reverse clutch 51 are disconnected. When the input shaft 1 is rotated under the state, power is transmitted from the input shaft 1 to the output shaft 37a by the transmitting shaft 50 and the planetary gear type transmission 25a. That is, when the input shaft 1 is rotated in running at high speed as described above, the rotation is transmitted to the ring gear 41 via the high speed clutch 40a and the transmitting shaft 50. Further, rotation of the ring gear 41 is transmitted to the sun gear 45 via the plurality of sets of planetary gear elements 46a and 46b to rotate the output shaft 37a fixed with the sun gear 45. When revolving speed of the respective planetary gear elements 46a and 46b is changed by changing the transmission ratio of the toroidal-type continuously variable transmission 24a, a transmission ratio of a total of the continuously variable transmission apparatus can be controlled.
That is, in the high speed mode state, the slower the revolving speed of the respective planetary gear elements 46a and 46b, the faster becomes the rotating speed of the output shaft 37a fixed with the sun gear 45. Therefore, in the high speed mode state, the more changed the transmission ratio of the toroidal-type continuously variable transmission 24a to a speed reducing side, the more changed is the transmission ratio of the total of the continuously variable transmission apparatus to a speed increasing side. In such a state of running at high speed, the toroidal-type continuously variable transmission 24a is applied with the torque not from the input side disk 2 but from the output side disk 5 (applied with a minus torque when the torque applied at low speed is constituted by a plus torque). That is, in the state of connecting the high speed clutch 40a, the torque transmitted from the engine 42 to the input shaft 1 is transmitted to the ring gear 41 of the planetary gear type transmission 24a via the transmitting shaft 50. Therefore, a torque transmitted from the side of the input shaft 1 to the respective input side disks 2, 2 constituting the toroidal-type continuously variable transmission 24a is almost nullified.
Meanwhile, a portion of the torque transmitted to the ring gear 41 via the transmitting shaft 50 is transmitted from the respective planetary gear elements 46a and 46b to the respective output side disks 5, 5 via the carrier 47 and the first power transmitting mechanism 48. In this way, the more changed is the transmission ratio of the toroidal-type continuously variable transmission 24a to the speed reducing side, the smaller the torque applied from the output side disks 5, 5 to the toroidal-type continuously variable transmission 24a in order to change the transmission ratio of the total of the continuously variable transmission apparatus to the speed increasing side. As a result, in running at high speed, the torque inputted to the toroidal-type continuously variable transmission 24a is reduced, a transmitting efficiency of the total of the continuously variable transmission apparatus is increased, and durability of constituent parts of the toroidal-type continuously variable transmission 24a can be promoted. In accelerating or running at constant speed under the high speed mode state, the torque passing the toroidal-type continuously variable transmission 24a is transmitted from the respective output side disks 5, 5 to the respective input side disks 2, 2 via the respective power rollers.
Further, when the output shaft 37a is rotated reversely in order to back up the automobile, both of the low speed and the high speed clutches 39a and 40a are disconnected and the reverse clutch 51 is connected. As a result, the ring gear 41 is fixed, and the respective planetary gear elements 46a and 46b are revolved at a surrounding of the sun gear 45 while being brought in mesh with the ring gear 41 and the sun gear 45. Further, the sun gear 45 and the output shaft 37a fixed with the sun gear 45 are rotated in a direction reverse to that in running at low speed, mentioned above, and in running at high speed, mentioned above.
In the case of the continuously variable transmission apparatus constituted by combining the toroidal-type continuously variable transmission 24 or 24a and the planetary gear type transmission 25 or 25a via the clutch apparatus and having the low speed mode and the high speed mode, regardless of whether the continuously variable transmission apparatus is constituted by the above-described geared neutral type or the above-described power split type, in switching the low speed mode and the high speed mode, the magnitude and the direction of the torque passing the toroidal-type continuously variable transmission 24 or 24a are rapidly changed. Meanwhile, respective constituent members of the toroidal-type continuously variable transmission 24 or 24a is displaced or elastically deformed in a direction in accordance with the direction of the torque in accordance with the magnitude of the torque passing the apparatus (passing torque). Further, in accordance with the displacement or the elastic deformation, there is produced so-to-speak torque shift in which the transmission ratio of the toroidal-type continuously variable transmission 24 or 24a is changed.
Therefore, when any measure is not taken therefor, in switching the modes of the continuously variable transmission apparatus, the transmission ratio of the total of the continuously variable transmission apparatus is rapidly varied by the torque shift. When the transmission ratio is varied in this way, a speed change shock is brought about to give unpleasant feeling to a passenger starting from a driver and to cause to deteriorate a part of a system of transmitting power and therefore, the rapid variation is not preferable. In contrast thereto, there is disclosed a technology of preventing rapid variation of the gear ratio in switching the mode in U.S. Pat. No. 6,074,320, JP-A-2001-50375, JP-A-2001-50380, JP-A-2001-235022, and U.S. Pat. No. 6,569,051, which have been known conventionally.
Among them, according to a prior art described in U.S. Pat. No. 6,074,320, the mode is switched in a state in which a rotating speed of power inputted to a planetary gear type transmission via a toroidal-type continuously variable transmission and a rotating speed of power inputted to the planetary gear type transmission without passing the toroidal-type continuously variable transmission coincide with each other. Further, according to prior arts described in JP-A-2001-50375, JP-A-2001-50380 and JP-A-2001-235022, in switching modes, connection and disconnection of respective clutches are switched in semi-clutched state. Further, according to the prior art described in U.S. Pat. No. 6,569,051, modes are switched by electromagnetic clutches.
According to the prior art preventing rapid variation of the transmission ratio in switching modes in which modes are switched in the state in which the rotating speeds coincide with each other as disclosed in U.S. Pat. No. 6,074,320, the rapid variation of the transmission ratio based on the torque shift cannot be prevented only thereby. Further, in the case of switching connection and disconnection of the respective clutches in the semi-clutched state as disclosed in JP-A-2001-50375, JP-A-2001-50380 and JP-A-2001-235022, a delicate control is needed, a total of the apparatus is complicated, cost is increased and also danger of failure is enhanced. Further, in the case of switching modes by the electromagnetic clutches disclosed in U.S. Pat. No. 6,069,051, not only rapid variation of the transmission ratio based on the torque shift cannot be prevented only thereby but also danger of failure is enhanced.